1. Field of the Invention
The present invention relates to a communication device and a communication method of the same. Particularly, the communication device relates to a device that uses one global address as a representative of global IPv4 (Internet Protocol version 4) addresses, shares and manages the representative global address, and makes a relay between a WEB client located in a global space and a plurality of WEB servers located in a local space. Further, the communication method relates to an address sharing communication procedure in the case of using one global address as a representative of global IPv4 addresses, sharing and managing the representative global address, and making a relay between a WEB client located in a global space and a plurality of WEB servers located in a local space.
2. Description of the Related Art
Generally, when a WEB client uses various applications via an IP network, the WEB client makes a peer-to-peer connection with a WEB server that stores an application via the IP network and communicates therewith in the global space. In such a connection, an IP address is assigned to the WEB server with respect to each application for identification. Further, the WEB server is often mounted for each application that executes program processing. Accordingly, the number of WEB servers is on the increase in the global spaces and the local spaces. The increase raises concerns about the exhaustion of IPv4 addresses. Thus, there is an increasing demand for sharing a single IP address among a plurality of WEB servers.
In order to meet such a demand, a gateway device with a given function incorporates a large-scale data center and uses high-volume memory, and therefore the gateway device with a certain function becomes very expensive. The given function is a NAT (Network Address Translator) function which is proposed in RFC (Request For Comments) 1631 as a means to solve the lack of network addresses.
Specifically, a plurality of WEB servers to which local IP addresses or private IP addresses are assigned are connected to a local network (LAN). Hereinafter, a global IP address and a local IP address are referred to as a global address and a local address, respectively, for simplification. The NAT function communicates with a device that has an external global address by making shared use of a single global address for the respective WEB servers.
A device that performs address translation with use of the NAT function has been proposed. Japanese Unexamined Patent Application Publication No. 2002-152260 discloses a communication device with address translation function and a multimedia communication method, and Japanese Unexamined Patent Application Publication No. 2003-324482 discloses a gateway device with address translation function and an address translation method of the same.
In such a case, it is desirable to use the gateway device with the given function as described in M. Holdrege, “RFC2663-IP Network Address Translator (NAT) Terminology and Consideration”, [online], Internet Association Japan, August 1998, [Searched on Sep. 10, 2009], Internet <URL:http://www.faqs.org/rfcs/rfc2663.html>. The gateway device with the given function has a function that terminates a TCP (Transmission Control Protocol) connection with an HTTP (Hyper-Text Transfer Protocol) client, analyzes an HTTP message and transfers it.
Further, IP masquerade or NAPT (Network Address Port Translation) is one of address translation methods. It is a similar function to the above-described NAT, and a different point is that NAPT translates a port number of TCP/UDP (Transmission Control Protocol/User Datagram Protocol) in addition to an IP address. By the translation function, a plurality of communication terminal devices or WEB servers on a LAN (Local Area Network) can establish an Internet connection by the simultaneous shared use of a single IP address.
However, it is known that a multimedia application is unable to communicate when using the IP masquerade.
As described above, communication up to the network layer in a one-to-many connection between a single device connected to a network in the global space and a plurality of devices connected to a network in the private space has been achieved until now. However, it should be noted that the IP masquerade is designed so as to efficiently achieve one-way communication that makes concurrent access from a plurality of devices connected to a network in the local space to a single device connected to a network in the global space. The NAT function only specifies one-to-one address translation between a device in the global space and a device in the private space.